Water-flooding extraction is a main oil field exploitation method in China. However, long-term water-flooding extraction in oil fields results in aggravated non-homogeneity of the strata, accelerated water cut rising and degraded water flooding efficiency or inefficient circulation in the middle and late stages of oil field exploitation. Consequently, a great deal of oil remaining in the strata can't be recovered. Therefore, improving deep mining of the remaining oil is a key to increase and stabilize the yield in water-flooding extraction in oil fields in the middle and late stages. Improving the swept volume of oil displacement agents and improving the oil displacement efficiency of oil displacement agents are two approaches for water-cut control and production stabilization in oil fields at present. Chemical oil displacement techniques that mainly employ a polymer oil displacement system, polymer/surfactant binary composite oil displacement system, or polymer/surfactant/alkali ternary composite oil displacement system are important technical means for deep mining of the remaining oil, and have been successfully applied in field operations. The main functions of the polymer in a polymer oil displacement system or a composite oil displacement system established on the basis of a polymer are to increase the viscosity of the displacement fluid and alter the water-oil mobility ratio, so as to expand the swept volume and improve the oil recovery factor. Adding a surfactant into a polymer-based binary composite oil displacement system can decrease oil-water interfacial tension, modify wettability of rock surface, facilitate crude oil stripping from rock surface, improve oil displacement efficiency, and, in combination with the mobility modification ability of the polymer, greatly improve the oil recovery factor. For a polymer-based ternary composite oil displacement system, adding alkali can further enhance the oil displacement effect. The alkali added into the system can react with petroleum acids to produce surfactant and work with the added surfactant to improve the oil displacement efficiency of the composite oil displacement system. Furthermore, emulsified crude oil can be formed as a result of addition of the alkali, and thereby the viscosity of the displacement medium can be improved, and the mobility regulation and control ability of the polymer can be further improved. Field application results indicate that the oil recovery factor can be improved by more than 10% with polymer oil displacement techniques and polymer-based composite oil displacement techniques. However, some problems have occurred in field implementation of the above-mentioned techniques. For example, in a polymer oil displacement system or polymer-based composite oil displacement system, the viscosity of the polymer is severely decreased and the mobility control ability of the polymer is weakened under severe influences of the shearing action of the injection equipment and porous media in the strata and the physicochemical properties of the strata. Especially, in the follow-up water flooding stage, the injection pressure drops quickly, and the oil displacement agent may rush into the oil well easily. Consequently, the oil displacement effect of the oil displacement agent is severely limited, the service value of the oil displacement agent is decreased, and it is difficult to attain a long-time effective exploitation effect.